Paris: Olympic 4x100 freestyle relay champion Clement Lefert has quit swimming to go back to university, saying he will not be able to make a living out of his sport.

"I have put an end to my career to focus entirely on my studies," the 24-year-old Lefert said on Friday.

"I did not take this decision overnight. I have been considering it for a while because I always worried about my future."

Lefert, who also took a 4x200 freestyle relay silver medal at the London Games, said he wanted a bright professional future and had enrolled at business school EDHEC, one of the best in France.

"I want to have a job I like, not one I would not have chosen and I am fully aware that swimming will never make me free from want," he said.

"I am not Camille Lacourt, Yannick Agnel or Laure Manaudou," he said, referring to the few French swimmers who clinched lucrative advertising contracts after they won world or Olympic titles.

Manaudou, who was the 2004 Olympic 400m freestyle champion but failed to get into a final in London, gets 1.5 million euros (USD 1.93 million) a year from sponsors, according to daily newspaper Le Parisien.

By comparison, American swimmer Michael Phelps, the world's most decorated Olympic athlete, has been earning five to seven million dollars a year since the 2008 Beijing Olympics, according to media reports.